Lithographic plate



United States Patent 3,261,285 LITHGGRAPHIC PLATE Jack L. Sorkin, Cleveland Heights, Ohio, assignor to Harris-Intertype Corporation, Cleveland, Ohio, a corporation of Delaware No Drawing. Filed Mar. 9, 1962, Ser. No. 178,556 Claims. (Cl. 101-.-149.2)

The present invention relates to a lithographic plate and, more particularly, to a novel barrier layer or sublayer which is interposed between the support member and a sensitizer, such as a diazo sensitizer.

In the preparation of a lithographic printing surface, it is known to provide a hydrophilic sub-layer between a backing or support member and a light-sensitive coat. Subsequently, selected areas of the light-sensitive coat are exposed to light, as through a stencil or negative or positive transparency, and the plate then developed in a manner known in the art. In so doing, predetermined areas of the light-sensitive coat are removed, depending on whether a positive or negative working type of light-sensit-ive agent is used, revealing corresponding underlying areas 'of the sub-layer. In practice the exposed portions of the sub-layer form the non-printing areas of the plate and, due to their hydrophilic nature, inhibit scumming and thereby prolong the press life of the resulting lithographic plate.

The use of diazo sensitizers, especially those of the negative working type, has become popular in recent years although, particularly in the case of this type of light-sensitizer, a barrier or sub-layer between a metal plate and the diazo is needed since, as is well known, direct contact with the metal destroys the diazo compoundv for lithographic purposes. Diazo sensitizers are commeroially attractive because a completed presensitized plate may be prepared which can be stored in light-tight packages for several months prior to use. At that time the plate is converted to a printing plate or surface by exposure to a light source through a negative, stencil, transparency, or the like, followed by washing with a developer, usually water. However, even presensitized plates have a limited guaranteed storage life which may be as short as six months or less. It is sometimes necessary to store plates for longer periods than this. In particular, printers who purchase in relatively large quantities must store some plates for relatively long periods of time prior to use and therefore cannot always use the presensitized type of plate.

For such printers, a plate is prepared having a desired hydrophilic sub-layer but lacking an overlying light-sensitive coat. At the time of use, the printer merely swabs or wipes on a solution of a sensitizer and dries the plate which is then ready for exposure. Accordingly, such plates having only a sub-layer are known in the art as wipe-on plates. However, since the hydrophilic layer is exposed in such a plate and is not protected by an overlying layer of a sensitizer, as in the case of a presensitized plate, the sub-layer deteriorates in time and loses its hydrophilic character. Consequently, even in the case of presently known wipe-on plates, there is a time limitation as to use.

The present invention is based on an improved sublayer or barrier for lithographic plates where in the preferred form a metal ester is incorporated with a methacrylato chromic halide and an acrylic compound, at least the last two components being interreacted as hereinafter described. Desirably, the sub-layer or barrier, formed over a support member, comprises multi-layers or strata. In this embodiment, a relatively thick sub-layer can be formed by varying the thickness of the different layers,

I, such as the layer formed from the halide, and thereby amply protect any sensitizer such as a diazo resin from being destroyed through chemical reaction with a metal sheet or plate. A still further control on the thickness of the barrier layer is afforded by regulating the amount or depth of reaction between a layer of the acrylic compound and a layer of the halide compound.

The support member and overlying sub-layer may be shipped as such in the form of a wipe-on plate or, at any time desired, any of the known lithographic sensitizers may be applied. The plate is then exposed to light and washed with a developer, such as water, in a manner known in the art.

It is, therefore, a principal object of the present invention to provide an improved lithographic plate and a process for preparing it.

Another object is to provide a lithographic plate having an improved sub-layer.

A further object is to provide a substantially permanently hydrophilic sub-layer, particularly adapted for use with wipe-on plates.

A still further object is to provide an improved presensitized lithographic plate.

A still further object is to provide a metal-surfaced lithographic plate having a multi-layer barrier, each layer being chemically reacted with adjacent layers and the 'bottommost layer being chemically reacted as well with the metal surface of the plate.

Other objects of the invention will become apparent as the description proceeds.

To the accomplishment of the foregoing and related ends, the invention consists of the features hereinafter fully described and particularly pointed out in the claims, the following disclosure describing in detail the invention, such disclosure illustrating, however, but one or more of the various ways in which the invention may be practiced.

GENERAL CONCEPT In accordance with the present invention, a sub-layer or barrier is formed from an alkacrylato chromic halide and an acrylic compound over a support or backing member of a lithographic plate. In the prefer-red practice a third component, a metal ester, is included. These components can be applied to a support member in a variety of ways. The two components (the halide and acrylic compound) or the three components can be applied in admixtures; or the halide can be applied alone with a subsequent overlay of the acrylic compound; or the metal ester and halide may be applied in admixture with a similar subsequent overlay of the acrylic compound; or the three components may be applied as individual layers. In any event, whether two or three components are chosen, these components interreact to form a barrier layer. When superposed layers of the ingredients are used, there is reaction between adjacent layers. When the support member is metal-surfaced or is composed of a resinous material such as a polyester or polyamide resin, there is also reaction with such metal or resin. After formation of the sub-layer, a conventional lithographic sensitizer may be applied and the plate exposed to light and developed in a manner known in the art.

COMPONENTS The metal esters contemplated are those having the formula, (RO) M, wherein R is a monovalent hydrocarbon radical selected from the group consisting of aryl radicals, such as phenyl, tolyl, xylyl; and all aliphatic radicals of one to eight carbon atoms, including alkyl, isoalkyl, alkylene, isoalkylene, alkenyl, isoalkenyl radicals, that is, without regard to degree of saturation or spatial isomerism; and wherein M is titanium or zirconium. The metal thorium has become more available, in recent years and has the same chemical behavior characteristics as titanium and zirconium and therefore M may also be thorium. However, titanium and zirconium are preferred. Such compounds, regardless of the metal used, are commonly referred to as metal ortho esters and also as alcoholates or phenylates. The tetraalkyl metal esters are preferred and of these tetraisopropyl titanate is preferred.

The manner of preparing these materials, hereinafter for convenience referred to as the ester, is known in the art. Reference is made, for example, to United States Patent No. 2,187,821 which is hereby incorporated by reference. As described, one method of preparation comprises, for instance, reacting an alcohol with a halide, preferably the chloride, of titanium in the presence of ammonia.

The alkacrylato chromic halides contemplated by the present invention include methacrylato and ethacrylato chromic halides. The former is preferred. These materials are Werner type compounds in which methacrylic acid or ethacrylic acid is coordinated with chromium to form a highly reactive complex. In the case of methacrylic acid, the following general structural configuration results:

wherein R is a halogen such as chlorine, iodine, or bromine. The complex is similar in the event ethacrylic acid is used, the ethyl group replacing the methyl group in the complex. When reference is hereinafter made to methacrylato groups, such reference is by way of example only and is taken to include similarly ethacrylato groups" as part of the defined chromic halide. When applied to a surface, especially a negatively charged surface, the chromium complex is strongly held. In addition, the complex contains a reactive organic group which can combine with the vinyl moiety of the acrylic compound as hereinafter described.

With an effective removal of the halogen atoms, as for example by ionization, the Werner chromium complex forms polymers by interreaction between a chromium atom and a hydroxyl group. This forms an oxygen bridge connecting two or more of the complexes. Similarly, the chromium atoms of the complex may react with active atoms on the surface to which the complex is applied, such as active oxygen atoms, to bond the chromium chemically to such surface. Even where the surface to be treated does not have a sufficient quantity of reactive atoms or groups to react with the chromium atoms, the chromium polymers may still strongly be held by electrostatic forces. Thus, a polymerized and bonded complex of the type herein contemplated may be generally represented as follows, continuing the example of methacrylato chromic halide. Actually, each chromium atom is probably associated with six atoms of either oxygen or nitrogen in a three dimensional network.

The acrylic compounds useful in practicing the present invention are the water-soluble organic aliphatic acrylic compounds. Specific examples include acrylic acid, methacrylic acid, the Watensoluble salts of such acids, such as the ammonium, sodium, and potassium salts, acrylamide, and methyl acrylamide. As used here and in the claims, the term acrylic compound is taken to include such acrylic compounds whether in monomeric or polymeric form. Insofar as application in accordance with the present invention is concerned, whether a monomer or polymer is chosen is largely a matter of desired or permissible chemical reactivity of the acrylic compound with the defined halide or polymer formed therefrom. The monomeric acrylic compounds are chemically more reactive than the polymers and therefore are usually preferred. However, while polymers of any of the acrylic compounds may be used, some acrylic compounds in particular may polymerize on standing or are otherwise difficult to obtain in pure monomeric form. As long as the polymeric growth is not suflicient to render the polymerized acrylic compound substantially non-reactive with the halide or its polymer, such acrylic polymers may be employed.

Ordinarily, the support member of the lithographic plate is metal-surfaced or entire sheets of metal may be used. This practice is preferable since a direct chemical union is then achieved between the metal and the sublayer to form a strong bond therebetween. Metals such as aluminum, zinc, copper, chromium, tin, magnesium, steel, and the like may be used. Aluminum and zinc are preferred. However, other supports or backing members may be employed, and in this instance the other advantages of the present sub-layer are retained. For example, a paper sheet or plate suitably hacked, or the paper sheet impregnated with a thermosetting resin such as phenol formaldehyde can be employed. In these instances, the sub-layer is also bonded to the paper or its resin impregnant but adheres thereto in the manner of a paste and may not chemically unite with this type of backing member. However, should a paper surface or resin impregnant have active chemical groups, such as hydroxyl groups (as in the case of a polyester resin), there may also be reaction between the components of the invention and such active groups. A heat-resistant resin impregnant is preferably employed, since it protects the paper during the heating steps which may be used in preparing a lithographic plate in accordance with the method disclosed herein. In the case of metallic surfaces, oxides may be present, either through exposure to air or through special treatment. For example, in the case of aluminum, the surface may if desired be chemically or electrolytically anodized, although this is not necessary. Also in the case of metallic surfaces, pretreatments may, if desired, be carried out to hydroxylate or oxidize followed by hydration of the metal surface and thereby facilitate chemical reaction of such surface particularly with the metal esters. This concept is described and claimed in greater detail in application Serial No. 74,780, filed in the names of Sorkin and Thomas. This application is hereby incorporated by reference.

The lithographic sensitizer or light-sensitive agent employed may be any of those known in the art for use on a surface lithographic plate, the present invention residing in the sub-layer and not being related to any particular light-sensitive agent used. Both negative and positive working sensitizers rare [contemplated for the present surface pl ates. For example, commonly known tannable colloids and tanning agents may be used. These include bichromated albumin, casein, gum arabic, gelatin, glue, a copolymer of polyvinyl-methylether and maleic anhydride, polyvinyl alcohol, and the like. In all of such cases, as is understood in the art, hexavalent chromium ions chemically react with the companion material, such as casein, under the action of light to alter the watersolubility of the coating and delineate printing and nonprinting areas of the plate. This action of the chromium ion is thus well known in the. art and may be provided by 'adding ammonium chnom-ate or dichromate, sodium chromate or dichromate, potassium chromate or dichromate, and the like. In addition to these, certain organic chnomates and dichromates may also be used. For example, the reaction product of a quaternary ammonium hydroxide and chromic acid, or ethylene diamine and chromic acid or a soluble dichromate may be employed. Such organic materials may be advantageous in that they show less tendency to crystallize and therefore produce a more uniform sensitized coating. Diazo compounds such as the condensation product of parafo-rmaldehyde with pdiazo-diphenylamine sulfate may also be used as a tanning agent in combination with the mentioned colloids.

Additionally, for the lithographic sensitizer the polymeric cinnamic acid esters of US. Patent No. 2,610,120; or the light-sensitive polymers of US. Patent No. 2,861,058; or the light-sensitive high molecular compounds of US. Patent No. 2,948,706 may be used. These three patents are also incorporated by reference.

A diazo compound such as is commonly used in the preparation of presensitized lithographic plates may be used per so as the sensitizer. It is emphasized that the nature of the diazo material is not critcal to the practice of the invention. Accordingly, the light-sensitive diazo or diazide may be either of the coupling or non-coupling types or of the positive or negative working types.

Descriptions of the various diazo sensitizers which may be used are set forth in the following United States patents which are hereby incorporated by reference; Nos. 2,063,631, 2,100,063, 2,667,415, 2,679,498, 2,692,827,

2,772,972, and 2,778,735.

A method of preparing a very satisfactory diazo is described in Patent No. 2,679,498 and in Patent No. 2,100,063. This compound is a condensation product of paraforrnaldehyde with p-diazo-diphenylamine sulfate. Upon exposure to light, such as ultra-violet light, this type of light-sensitive diazo compound expels nitrogen from the molecule and forms a Water-insoluble, hydrophobic and oleophilic material which then becomes the printing image. The unexposed portions of the compound are readily washed away by known developer solutions, usually water.

PREPARATION In general, whether the defined components are applied in admixture or singly, such components are applied to a support member from a solvent followed by evaporation to remove the solvent and deposit a component or components as a layer. Organic solvents may always be used, and in the case of applying the halide alone or the acrylic component alone or just these two components in admixture, Water may additionally be used as the solvent for these two components. The use of heat hastens the evaporation and promotes the desired chemical reaction and is, therefore, preferably used except in the case where the metal ester is applied singly. In this instance, merely drying the plate as by whirling promotes the desired result. As a further aid in promoting the desired chemical reaction and reducing the time required for preparation, catalysts may also be incorporated with the solvent for a component or components.

In the case Where the halide and acrylic compound are applied in admixture, water may be used as the solvent or organic solvents may be used such as aromatic solvents like toluene, benzene, and xylene; alcohols like methanol, ethanol, propanol, and isopropanol; aliphatic solvents like pentane, hexane, and heptane; and chlorinated aliphatic solvents such. as carbon tetrachloride, and the like. In the case where the h'alide, ester, and acrylic components are applied in admixture, only the organic solvents as just mentioned may be used. Reliative amounts are not critical. Upper limits are set by the solubility of a component in a particular solvent. Recommended ranges by weight percent in the solvent include about 0.1 percent to about 10 percent for each component, namely, the ester, the halide, and the acrylic components. Various ratios may be used, but a preferred ratio is equal molar weight of the two or three components. In any event there should be sufficient acrylic component to react with the methaorylato or ethacrylato groups of the halide or its polymer as described. Any known method of coating suitable for providing a substantially uniform coat may be used such as, for example, roller coating, blade coating, dipping, whirling, or spraying. Such methods of coating may be used for any of the applications or coating steps herein described.

Following the application of the admixture, the plate is allowed to dry. However, heat, as from infrared lamps, is preferably used to remove the solvent and effect the interreaction of the components which results in a deposition of a barrier layer. Temperatures of about C. to about 210 C. for about 5 minutes to about 16 hours may be used. The exact mechanism involved among the three components is not known, although there is polymerization of the halide as described and reaction with the methacrylato groups thereof with the acrylic component. The metal ester hydrolyzes readily and absorbs moisture from the atmosphere for this purpose if none is otherwise available. When so hydrolyzed, the ester is quite reactive chemically through the resulting hydroxyl groups. When a metal or a reactive resinous material, as

previously described, comprises the surface of the lithographic plate, there is also chemical reaction therewith resulting in a strongly adhered barrier layer.

In one embodiment of the invention, the metal ester and halide are applied to the plate in admixture and a layer of their reaction product then deposited on the plate. This reaction product layer is next contacted with the acrylic component. This technique has the advantage of orienting the hydrophilic polar group of the acrylic component at the outer surface of the sub-layer.

The solvent for the ester and the halide may be any of those organic solvents noted for the admixture. While relative amounts are not critical, ranges by weight percent in the solvent of about 0.1 percent to about 10 percent for each the ester and the halide are operable. A sufficient amount of a catalyst may also be present in the solvent to speed the reaction, although a catalyst is not necessary in view of the presence of the metal ester. A concentration of catalyst of one percent or less by weight has been found to be satisfactory. This range is not critical. Catalysts that may be used include ammonium hydroxide, ethanolamine, diethanolamine, triethanolamine,

' dimethylaniline, and diethylaniline.

Following application of the ester-halide mixture, the plate is dried as before, preferably with heat. The solvent is evaporated and a barrier layer formed from the ester-halide mixture is deposited over the plate. Temperatures of about 130 C. to about C. for about five minutes to about two hours may be used to deposit the barrier layer. Again there is polymerization of the Werner complex, although the methacrylato groups of the latter remain unreacted. Again, also, the ester hydro- -lyzes and aids the reaction by its active hydroxyl groups,

particularly the reaction with a metal plate. It has also been postulated that the metal ester may act as a catalyst for the desired reaction and polymerization. Even in this instance, the metal ester acts not only as a catalyst for the polymerization but actually forms part of the final product, so that a complex-metal copolymer may be formed, especially when the metal ester and the halide are deposited from the same solution.

After the ester-Werner complex layer has been deposited, the acrylic component is applied thereover. If penetration of the complex polymer is desired, the solvent for the acrylic compound must be compatible therewith, that is, the solvent must be unreactive with the Werner complex polymer and capable of soaking into it. As used here and in the claims, the term compatible solvent is intended to have this definition.

By penetrating the complex polymer film, the solvent facilitates the acrylic compound in reaching the methacrylato groups of that polymer for reaction therewith. Inasmuch as the layer of the Werner complex polymer has been chemically anchored to the metal by the preceding treatment, this layer cannot be lifted from the metal surface by any solvent used for the acrylic compound. The amount of penetration and resulting stratification of the Werner complex layer by the solvent and interreaction between the layer and acrylic compound can be varied by the temperature and time of contact by the acrylic compound solvent with such layer. Indeed, there may be little or no penetration with only an interfacial reaction between the layer and the acrylic compound.

The solvent for the acrylic compound or component may be selected from the following: benzene, toluene, xylene, pyridene, petroleum ether, methanol, ethanol, butanol, monoalkyl ethers of ethylene glycol (Cellosolve) such as the methyl, ethyl, butyl, and isobutyl ethers of ethylene glycol, chloroform, carbon tetrachloride, and the like. It is necessary only that the acrylic component be sufficiently soluble in a selected solvent to be applied to a plate in a manner described. For example, about 0.7 gram of sodium acrylate dissolves in about 100 grams of 99 percent ethyl alcohol at room temperature. This is sufiicient for purposes of the invention. Water may also be the solvent for the acrylic component as hereinafter described.

The concentration of the acrylic component in the chosen solvent is not critical. An amount sufficient to cover the Werner complex layer to an extent desired may be initially incorporated in the solvent. As an example, the concentration may range from about 1 percent to percent, although concentrations outside of this range may be employed, repeated applications being carried out if needed. A sufficient amount of a catalyst may also be incorporated with the acrylic component. The free radical-forming catalysts such as benzoyl peroxide, acetyl peroxide, urea peroxide, hydrogen peroxide, cumene hydroperoxide, potassium persulfate, and the like are usable. The catalysts may be dispersed in the solvent for the acrylic compound if necessary. An exemplary range which may be used for the catalyst is up to one percent by weight of the solution.

The heating effecting the reaction between the Werner complex layer and the acrylic compound should be continued for a sufficient time to ensure reaction between the methacrylato groups of the former and the acrylic component. This reaction is hereby defined as heating to produce a hydrophilic stable copolymer, the term stable referring to the chemical stability of the copolymer with respect to a sensitizer. The time and temperature required for so properly effecting the reaction is readily determined by trial and error runs. The rate of the reaction is affected by the temperature, catalyst, and concentration of catalyst employed. The recommended temperature range for reacting the Werner complex layer and acrylic component is from about 120 C. to 300 C. for 10 minutes to 12 hours. However, higher temperatures may be employed. Any temperature limit may, in fact, be set by practical considerations, such as avoiding a temperature sufiiciently high to anneal the metal of the lithographic plate. It is also recommended to raise the temperature of the reaction, either initially or terminally of this step, above the boiling point of the solvent for the acrylic compound to ensure vaporization and removal of traces of the solvent. Heating the reactants for 8 to 10 hours at 160 C. has worked satisfactorily, although heating for a longer time at a lower temperature and heating for a shorter time at a higher temperature are also operative.

An important advantage of the present sub-layer material is that should it be heated too long or dried from other causes, it does not crack and its hydrophilic character can be quickly restored by allowing the material to absorb or otherwise soak up water. This sub-layer material, therefore, does not deteriorate in the manner of a siliceous sub-layer.

An exception to the use of an organic solvent for the acrylic component is possible if a reaction at substantially only the interface between the Werner complex layer and the acrylic component is acceptable. In this case, the acrylic component is applied from aqueous solution Which may, for example, contain about 0.1 percent to about 10 percent by weight of such component. To effect reaction with an acrylic component in an aqueous medium, the plate is immersed and retained in the water until the desired reaction between the Werner complex layer and the acrylic component is complete. Warming the aqueous solution hastens the reaction and correspondingly reduces the time required. If the solution is heated from about 30 C. to about C. with a plate or other support member immersed therein, the reaction may be carried out in about 5 to about 15 minutes. In particular, sub-layers have been deposited in the manner just described by immersing a plate for five minutes at 90 C. As will be noted, the use of an aqueous solvent for the acrylic component materially reduces the time and temperature requirements for producing a plate. This technique is therefore best suited for economical commercial production.

While little or no penetration of the Werner complex layer occurs when the acrylic component is applied from aqueous solvent, this practice has the advantages of being much less expensive, avoiding the problems of fumes and the like attending the use of organic solvents, while still providing a reaction product of the polymerized Werner complex and acrylic component which is well adhered to the sub-stratum or sub-strata of the barrier layer. In fact, the use of Water as the solvent for the acrylic component can so shorten the previous time-temperature requirements that, not withstanding the foregoing, it is within the contemplation of the invention to omit the metal ester, applying the acrylic component from aqueous solution as described over a Werner complex layer which has been applied singly to a support member in the manner previously described. Use of a water-solvent for the acrylic component enables the normal sequential steps of contacting the Werner complex layer with the acrylic component and heating the assembly to be performed simultaneously.

As another modification, the solvent for the acrylic component may contain a hydrophilic agent selected from the group consisting of carboxymethyl cellulose, carboxyethyl cellulose, and vinyl pyrrolidone to enhance the resulting hydrophilic character of the sub-layer. Such an agent may be present in amounts ranging from about 0.3 percent to 5 percent based on the weight of the acrylic component.

As indicated, the embodiment comprises a support member having a first layer formed from the metal ester and halide components with an additional layer comprising the reaction product of the first layer with the acrylic component represents a desirable practice of the invention. Lithographic plates prepared with this type of sub-layer give excellent prints, roll up well, and withstand storage in a humidity cabinet having a temperature of F. and a relative humidity of 70 percent for at least one week. Such plates have produced 40,000 impressions without failure.

In another embodiment, each of the defined components may be applied separately to the support member. In this instance, the metal ester is applied first. The organic solvent for the application of the ester also may vary Widely. Aromatic solvents such as benzene, toluene, and xylene may be used; also solvents such as acetone, methyl-ethyl ketone, tetrahydrofurane, and the chlorinated hydrocarbons may be used. But a preferred solvent for the metal ester when used alone comprises the humectants or hygroscopic solvents which absorb moisture from an ambient atmosphere. This action supplies a ready ource of water for the hydrolysis and literally boosts such hydrolysis. When the solvent employed is not a humectant, as in the case of toluene, the solvent must first be substantially removed after deposition on a plate before the hydrolysis of the ester can take place, thus delaying the hydrolysis of the metal ester. The humectant solvents include, for example, the anhydrous or substantially anhydrous alcohols, such as methyl, ethyl, propyl, isopropyl, butyl, and isobutyl alcohols, ethylene glycol, diethylene glycol, glycerol, Cellosolve, Cellosolve acetate, Cellosolve butylate, methyl Cellosolve, butyl Cellosolve, Carbitol, butyl Carbitol, and the like.

The solvent may contain from 0.1 percent to about 10 percent by weight of the ester. If desired titanates and zirconates (and thorates) can be used in combination. Following application of the ester solvent, the plate is dried as by whirling to deposit a layer of the hydrolyzed metal ester which in the case of a metal-surfaced plate, as an example, is chemically bound thereto. In this regard, the hydration of the ester may be permissive, that is, allowed to be affected by the moisture in the atmosphere. The hydrolysis mechanism is thought to involve the formation of an intermediate complex between the metal ester and the water. The hydroxy ester cannot be isolated since it immediately reacts to give a dimer. Thereafter, the halide and acrylic components may be applied in the order stated, using the solvents and conditions described for the immediately preceding embodiment.

When the halide is applied alone, an aqueous solution may be used. For general applications, a concentration in the range of 0.5 percent to 2 percent by weight is usually suitable. However, concentrations in the ranges of 0.1 percent to about 5 percent by weight may also be used. In order to obtain best results from treatment with the methacrylato chromic halide, it is advisable to neutralize partially the acidity of the solution of the complex with a suitable base. Nitrogeneous bases, and preferably ammonia, have been found useful for thi purpose. A dilute solution of the neutra-lizer is added to the halide solution with vigorous agitation in order to minimize local precipitation which occurs at pH values above seven. In general, the

' pH of the treating solution is adjusted to an initial value of between 5 and 6.5. This pH may drift toward a more acid pH as the solution ages.

It is generally preferred to immerse the plate to be treated in the neutralized solution of the halide, so that the plate is completely saturated with the treating solution. However, the halide solution may also be applied by any conventional means such as spraying, brushing, etc. The treated plate may be dried by any standard means. For example, it may be dried by an electric fan. It is advisable to dry the surface completely in order to set the chromium complex to an underlying substrate. However, heating to such an extent that some of the unsaturated groups are destroyed should of course be avoided.

Regardless of how the sub-layer or barrier layer is applied, the lithographic sensitizer is coated over such layer as a final step in preparing the plate. The sensitizer may be applied over the su-b layer in a conventional mannor as by roller coating, dipping, spraying, and the like.

A suflicient amount should be used to cover the entire sub-layer. The light-sensitive tanning agents form an image when exposed to light in accordance with techniques of lithographic operation. Negative-working diazo compounds are usually applied from an aqueous solution, while positive working diazos are usually applied from organic solvent as is known in the art. The thickness of the diazo film is not critical, a residue of about 0.003 gram per square foot of plate being an accepted practice. Aqueous solutions of up to about two percent diazo compound have also been employed.

If desired, the manufacturer of a lithographic plate of 10 the present invention can stop short of the application of the light-sensitive agent, so that a wipe-on plate having only the sub-layer can be shipped to a printer.

Examples In order to demonstrate the invention, the following examples are set forth for the purpose of illustration only.

.Any specific enumeration or detail mentioned should not be interpreted as a limitation of the invention unless specified as such in one or more of the appended claims and then only in such claim or claims.

Example I An aluminum plate was dipped into the following solution:

The plate was then baked for five minutes at 170 C. and washed with water for five minutes. A rotating rubber roller wet with a 0.8 percent diazo aqueous solution is rolled over the resulting sub layer to apply a continuous coating of the diazo solution. The diazo ma- 'terial use-d consisted essentially of a condensation product *of para-formaldehyde with p-diazodiphenylamine sulfate and is sold under the trade name Fairmont Diazo No. 4.

The plate was then dried by air currents from an electric fan.

Afiter exposing the .d'iazo sensitizer to light through a negative, the plate was developed by washing with water. The resulting plate printed many thousand impressions rbefore showing any tendency for the ink-attractive printing image to break.

Example II A zinc plate was dipped into a 10 percent by weight solution of tetraoctyl titanate in isopropanol and air dried. The plate was then dipped into a solution consisting of 180 cc. of methanol and 20 cc. of a 20 percent by weight aqueous solution of methacrylato chromic chloride. The plate was then baked for 10 minutes at 170 C. and subsequently immersed for 30 minutes in a solution comprising:

Acrylic acid (glacial), cc 10 Ethanol (anhydrous), cc. 990 Benzoyl peroxide, grams 0.1

' sensitized, and inked for printing in the usual manner.

The image held well and the background was clean.

Example III An aluminum plate was dipped into the following solution:

Benzene, cc. Tetra-n-octyl zirconate, grams l Methacrylato chromic chloride, grams 1 The plate was then air dried and baked for five minutes at C. The plate was next dipped into the following solution at room temperature:

Acrylamide, grams 10 Isopropanol (anhydrous), cc. 90 Urea peroxide, grams 0.1

The plate was again baked at 170 C., this time for minutes, and then washed with water for five minutes. An aqueous dispersion of bichromated casein is now blade coated over the resulting sub-layer to sensitize the plate which is then finally air dried. After exposure through a stencil in the usual manner followed by development, the plate was installed in a press and printed many thousand impressions before any image breakdown was noticeable.

Example IV A zinc plate was dipped into the following solution:

Cc. Methacrylato chromic chloride aqueous solution) 10 Tetraisopropyl titanate 10 Isopropanol (anhydrous) 90 Ammonium hydroxide (28% aqueous solution) 3 The plate was allowed to drain dry and then baked for five minutes at 170 C. The plate was then immersed for five minutes into the following solution maintained at least at 90 C.:

Water, cc. 100 Acrylic acid (glacial), cc 1 Ammonium persulfate, grams 0.02

The plate was washed with tap water for several minutes after which a bichromated gelatin colloidal dispersion was applied over the resulting barrier layer in an amount to cover a layer and form a film of suitable thickness for lithographic reproduction techniques.

Example V The following exemplifies a preferred practice of the invention. An aluminum sheet was immersed for 3 minutes at 70 C. in a 20 percent aqueous solution of trisodium phosphate to clean and etch the aluminum surface. This surface was then flushed with tap water for l minute and then desmutted by dipping for 2 minutes in a 70 percent nitric acid solution maintained at room temperature.- The plate was again flushed, first for 1 minute with tap water at room temperature and then for about 1 minute with deionized water, after which the plate was allowed to dry.

The plate was next dipped into an isopropanol solution containing 2 percent of methacrylato chromic chloride and 1 percent of tetraisopropyl titanate, such solution being at room temperature. The plate was then baked for five minutes at 150 C. to deposit a layer from the halide and titanate. After a rinse with tap water, the plate was next immersed tfor five minutes in an aqueous solution of 1 percent by weight of acrylic acid and 0.02 percent of ammonium persulfa-te. This solution was maintained at 90 C. After removal from the acrylic acid solution the plate was washed for five minutes with tap water and then for an additional minute with deionized water.

An aqueous solution containing 2 percent by weight of Fairmonts Diazo Resin No. 4 was then coated over the previous sub-layer preparation by means of a whirler. The plate thus prepared was allowed to dry and in this form could be stored or used immediately for exposure.

Plates prepared in this manner were store-d unsealed in a humidity cabinet having a temperature of 110 F. and a relative humidity of 72 percent. Testing up to two weeks showed these results:

Storage Results 12 Example VI A procedure was carried out like the procedure of Example V, except that the titanate was omitted. Instead, after cleaning the surface of the aluminum sheet a 20 percent by weight aqueous solution of methacrylato chromic chloride was initially used in preparing the subbase. The solution of the chloride was adjusted to a pH of 6 by ammonia. After application of this solution, the aluminum sheet was dried by whirling. The acrylic acid and diazo sensitizer were then sequentially applied as in Example V.

In any of the foregoing examples, equivalent compounds and solvents disclosed herein may be substituted for those stated in the examples, the times and temperatures being adjusted where and if needed as easily determined by trial and error.

Other forms embodying the features of the invention may be employed, change being made as regards the features herein disclosed, provided those stated by any of the following claims or the equivalent of such features be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A process of forming a sub-layer on a lithographic plate for reception of a light-sensitive material comprising applying to a support member a coat of an admixture comprising a halide selected from the group consisting of methacrylato chromic halide and ethacrylato chromic halide, and a water-soluble organic aliphatic acrylic compound, and interreacting such halide through its methacrylato or ethacrylato group with the acrylic component of the admixture to form on the support member a permanently hydrophilic sub-layer.

2. A process of preparing a wipe-on lithographic plate for reception of a light-sensitive material comprising coating a support member from organic solvent with an admixture of a halide selected from the group of methacrylato chromic halide and ethacrylato chromic halide, and an acrylic compound selected from the group consisting of acrylic acid, methacrylic acid, the ammonium, sodium, and potassium salts of said acids, acrylamide, methyl acrylamide, and polymers thereof reactive with such halide, and then heating to remove the solvent and interreact such halide through its methacrylato or ethacrylator group with the acrylic component of the admixture to deposit on the support member a permanently hydrophilic sub-layer.

3. A process of forming a sub-layer on a lithographic plate comprising applying to a support member a coat of a methacrylato chromic halide, applying over said coat a layer of an acrylic compound selected from the group consisting of acrylic acid, methacrylic acid, the ammonium, sodium, and potassium salts of said acids, acrylamide, and methyl acrylamide, and then reacting said coat with the acrylic compound.

4. A process of forming a sub-layer on a lithographic plate for reception of a light-sensitive material comprising applying to a support member a coat of an admixture comprising a halide selected from the group consisting of methacrylato chromic halide and ethacrylato chromic halide; a water-soluble organic aliphatic acrylic compound; and a metal ester having the formula, (RO) M, wherein R is a monovalent hydrocarbon radical selected from the group consisting of phenyl, tolyl, xylyl, and aliphatic radicals of one to eight carbon atoms, and M is a metal selected from the group consisting of titanium and zirconium; and interreacting such halide through its methacrylato or ethacrylato group with the acrylic compound and simultaneously reacting such metal ester with such halide and acrylic compound to form on the support member a permanently hydrophilic sub-layer.

5. A process of forming a sub-layer on a lithographic plate comprising applying to .a support member a coat of an admixture comprising a methacrylato chromic halide,

and a metal ester having the formula, (RO) M, wherein R is a monovalent hydrocarbon radical selected from the group consisting of phenyl, tolyl, xylyl, and aliphatic radicals of one to eight carbon atoms, and M is a metal selected from the group consisting of titanium and zirconium; interreacting such halide and metal ester to deposit on the support member a layer of the resulting reaction product; coating such layer with an acrylic compound selected from the group consisting of acrylic acid, methacrylic acid, the ammonium, sodium, and potassium salts of said acids, acrylamide, and methyl acrylamide; and then reacting the layer with the acrylic compound.

6. A process of preparing a wipe-on lithographic plate comprising directly coating a support member from organic solvent with an admixture of a methacrylato chromic halide and a metal ester having the formula, (RO) M, wherein R is a monovalent hydrocarbon radical selected from the group consisting of phenyl, tolyl, xylyl, and aliphatic radicals of one to eight carbon atoms, and M is a metal selected from the group consisting of titanium and zirconium; heating to remove the solvent and deposit as a layer on the support member a reaction product of such halide and metal ester; coating such layer from organic solvent with an acrylic compound selected from the group consisting of acrylic acid, methacrylic acid, the ammonium, sodium, and potassium salts of said acids, acrylamide, and methyl acrylamide; again heating to react such layer with the acrylic compound and deposit on the support member a hydrophilic barrier consisting essentially of the reaction product of such three reactants.

7. A process of forming a multi-layer barrier on a lithographic plate comprising applying to a support member a coat of a metal ester having the formula, (RO) M, wherein R is a monovalent hydrocarbon radical selected from the group consisting of phenyl, tolyl, xylyl, and aliphatic radicals of one to eight carbon atoms, and M is a metal selected from the group consisting of titanium and zirconium; hydrolyzing the metal ester to deposit a layer of such hydrolyzed metal ester over the support member; applying to the metal ester layer from solvent a methacrylato chromic halide; drying the halide application to form a second layer over the first layer; applying to the halide layer an acrylic compound selected from the group consisting of acrylic acid, methacrylic acid, the ammonium, sodium, and potassium salts of said acids, acrylamide, and methyl acrylamide; and reacting such second layer and acrylic compound to form a hydrophilic barrier on said plate.

8. A process of preparing a multi-layer barrier on a wipe-on lithographic plate comprising coating 2. support member from organic solvent with a metal ester having the formula, (RO) M, wherein R is a monovalent hydrocarbon radical selected from the group consisting of phenyl, tolyl, xylyl, and aliphatic radicals of one to eight car bon atoms, and M is a metal selected from the group consisting of titanium and zirconium; heating to remove the solvent; hydrolyzing the metal ester and adhering a layer of the hydrolyzed ester to the support member; applying to the metal ester layer from organic solvent a methacrylato chromic halide; heating to remove the halide solvent and polymerize the halide to form a second layer; applying to the second layer from a solvent an acrylic compound selected from the group consisting of acrylic acid, methacrylic acid, the ammonium, sodium, and potassium salts of said acids, acrylamide, and methyl acrylamide; heat-ing to remove the acrylic solvent and react the acrylic compound with the second layer; such superposed layers forming a hydrophilic barrier over the support member.

9. A process of forming a sub-layer on a lithographic plate for reception of a light-sensitive material comprising applying to a support member a metal ortho ester; a methacrylato chromic halide; and an acrylic compound selected from the group consisting of acrylic acid, methacrylic acid, the ammonium, sodium, and potassium salts l4 of said acids, acrylamide, methyl acrylamide and polymers thereof reactive with such ester and halide; and in terreacting such halide through its methacrylato group with the'acrylic compound and reacting such metal ester with such halide and acrylic compound to form on the support member a permanently hydrophilic sub-layer.

10. A process of forming a sub-layer on a lithographic plate for reception of a light-sensitive material comprising applying to a support member a metal ester having the formula, (RO) Th, wherein R is a monovalent hydrocarbon radical selected from the group consisting of phenyl, tolyl, Xylyl, and aliphatic radicals of one to eight carbon atoms; a methacrylato chromic halide; and an acrylic compound selected from the group consisting of acrylic acid, methacrylic acid, the ammonium, sodium, and potassium salts of said acids, acrylamide, and methyl acrylamide; and interreacting such metal ester with such halide and acrylic compound and interreacting such halide through its methacrylato group with the acrylic compound to form on the support member a permanently hydrophilic sub-layer.

11. A process of preparing a wipe-on lithographic plate comprising directly coating a support member from organic solvent with an admixture of a methacrylato chromic halide and a metal ester having the formula, (RO) M, wherein R is a monovalent hydrocarbon radical selected from the group consisting of phenyl, tolyl, Xylyl, and aliphatic radicals of one to eight carbon atoms, and M is a metal selected from the group consisting of titanium and zirconium; heating to remove the solvent and deposit as a layer on the support member a reaction product of such halide and metal ester; immersing the support member into an aqueous solution heated from about 30 C. to about C. of an acrylic compound selected from the group consisting of acrylic acid, methacrylic acid, the ammonium, sodium, and potassium salts of said acids, acrylamide, and methyl acrylamide to react such layer with the acrylic compound and deposit on the support member a hydrophilic barrier consisting essentially of the reaction product of such three reactants.

12. A process of preparing a wipe-on lithographic plate comprising coating a support member from organic solvent with a methacrylato chromic halide, heating to remove the halide solvent and form a layer of a methacrylato chromic polymer over and adhered to such support member, immersing the support member and adhered layer into an aqueous solution heated from about 30 C. to about 95 C. of an acrylic compound selected from the group consisting of acrylic acid, methacrylic acid, the ammonium, sodium, and potassium salts of said acids, acrylamide, and methyl acrylamide to react such polymeric layer with the acrylic compound.

13. A wipe-on lithographic plate comprising a support member and a hydrophilic barrier overlying the support member comprising the reaction product of a first layer overlying said support member of a halide selected from the group consisting of a methacrylato chromic halide and ethacrylato chromic halide with a second layer of a water-soluble organic aliphatic acrylic compound overlying said halide layer.

14. The wipe-on lithographic plate of claim 13 in which said acrylic compound is selected from the group consisting of acrylic acid, methacrylic acid, the ammonium, sodium, and potassium salts of said acids, acrylamide, methylacrylamide, and polymers thereof reactive with said halide.

15. A wipe-on lithographic plate comprising a support member and a permanently hydrophilic barrier layer overlying the support member adapted to receive a light-sensitive coating thereon; said barrier layer comprising the reaction product of a metal ester having the formula, (RO) M, wherein R is a monovalent hydrocarbon radical selected from the group consisting of phenyl, tolyl, Xylyl, and aliphatic radicals of one to eight carbon atoms, and M is a metal selected from the group consisting of titanium and zirconium; a halide selected from the group consisting of methacrylato chromic halide and ethacrylato chromic halide; and an acrylic compound selected from the group consisting of acrylic acid, methacrylic acid, the ammonium, sodium, and potassium salts of said acids, acrylamide, and methyl acrylamide said halide being reacted through its methacrylato or ethacrylato group With said acrylic compound.

References Cited by the Examiner UNITED STATES PATENTS 2,293,413 8/1942 Stoner et al 117-132 2,534,650 12/1950 Worthen 101-1492 Smith 117-132 Shoemaker et a1. 101-1492 Brinnick et a1 96-75 Mellan et a1 96-75 Dalton et a1 101-1492 Adams et a1 101-1492 X DAVID KLEIN, Primary Examiner.

10 ROBERT E. PULFREY, NORMAN G. TORCHIN,

Examiners.

ROBERT L. STONE, JANYCE A. BELL,

Assistant Examiners. 

2. A PROCESS OF PREPARING A WIPE-ON LITHOGRAPHIC PLATE FOR RECEPTION OF A LIGHT-SENSITIVE MATERIAL COMPRISING COATING A SUPPORT MEMBER FROM ORGANIC SOLVENT WITH AN ADMIXTURE OF A HALIDE SELECTED FROM THE GROUP OF METHACRYLATO CHROMIC HALIDE AND ETHACRYLATO CHROMIC HALIDE, AND AN ACRYLIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF ACRYLIC ACID, METHACRYLIC ACID, THE AMMONIUM, SODIUM, AND POTASSIUM SALTS OF SAID ACIDS, ACRYLAMIDE, METHYL ACRYLAMIDE, AND POLYMERS THEREOF REACTIVE WITH SUCH HALIDE, AND THEN HEATING TO REMOVE THE SOLVENT AND INTERREACT SUCH HALIDE THROUGH ITS METHACRYLATO OR ETHACRYLATOR GROUP WITH THE ACRYLIC COMPONENT OF THE ADMIXTURE TO DEPOSIT ON THE SUPPORT MEMBER A PERMANENTLY HYDROPHILIC SUB-LAYER.
 15. A WIPE-ON LITHOGRAPHIC PLATE COMPRISING A SUPPORT MEMBER AND A PERMANENTLY HYDROPHILIC BARRIER LAYER OVERLYING THE SUPPORT MEMBER ADAPTED TO RECEIVE A LIGHT-SENSITIVE COATING THEREON; SAID BARRIER LAYER COMPRISING THE REACTION PRODUCT OF A METAL ESTER HAVING THE FORMULA, (RO)4M, WHEREIN R IA A MONOVALENT HYDROCARBON RADICAL SELECTED FROM THE GROUP CONSISTING OF PHENYL, TOLYL, XYLYL, AND ALIPHATIC RADICALS OF ONE TO EIGHT CARBON ATOMS, AND M IS A METAL SELECTED FROM THE GROUP CONSISTING OF TITANIUM AND ZIRCONIUM; A HALIDE SELECTED FROM THE GROU CONSCONSISTING OF METHACRYLATO CHROMIC HALIDE AND ETHACRYLATO CHROMIC HALIDE; AND AN ACRYLIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF ACRYLIC ACID, METHACRYLIC ACID, THE AMMONIUM, SODIUM, AND POTASSIUM SALTS OF SAID ACIDS, ACRYLAMIDE, AND METHYL ACRYLAMIDE SAID HALIDE BEING REACTED THROUGH ITS METHACRYLATO OR ETHACRYLATO GROUP WITH SAID ACRYLIC COMPOUND. 